ABSTRACT The Microchemistry and Proteomics (MCP) Core provides mass spectrometric sequencing and quantitation of peptides and proteins to support basic, translational, and clinical research programs at MSK. The Core utilizes modern high-resolution mass spectrometry and nanoscale liquid chromatography in conjuction with biochemical processing of samples with the end goal of determining the identity, relative abundance, and presence of post translational modifications from purified components, cell lysates, tissues, and select fluid such as cerebral spinal fluid. Proteins and post translational modification are critical components of complex signaling pathways underlying development, cell growth, differentiation, DNA repair, senescence, immune response to cancer, and response to bioactive therapies. Dissection of these pathways can lead to insights on the underlying molecular mechanisms involved in cancer. The goal of the MCP Core is to be an efficient, user friendly, state-of-the-art facility. Advice is provided by the Core staff to facilitate the design, execution, and analysis of experiments. Over the past year, the Core has supported research from 38 investigators. Over the past grant period, investigators from all 10 programs have been supported, and the Core has contributed to 207 publications.